The brief will cover key EDB markets in Europe, North America and Asia. The appointment follows a review that started earlier this year.
The EDB is a government agency responsible for enhancing Singapore's position as a global business centre, helping grow the national economy and encouraging investment.
Angus Fraser, the JWT Singapore managing director, said the EDB challenge "requires an idea so big that it spills outside the boundaries of traditional advertising". He added: "The EDB is encouraging us to embrace new, thought-provoking ideas that do just that."